Generally, a terminal has different front-end configurations, respectively, according to a communication system determined when communicating with a base station, namely, the TDD system and the FDD system.
FIG. 1 is a general schematic diagram of a wireless transceiver system wherein the prior TDD system is applied.
As shown in FIG. 1, a TDD wireless transceiver system includes a modem 11, a first low pass filter 12, a local oscillator 13, a first mixer 14, a first band-pass filter 15, a power amplifier 16, a selecting switch 17, a second band-pass filter 18, and an antenna Ant, thereby constituting a transmission signal processing unit.
Also, the TDD wireless transceiver system includes an antenna Ant, a second band-pass filter 18, a selecting switch 17, a low-noise amplifier 19, a third band-pass filter 20, a second mixer 21, a local oscillator 22, and a second low pass filter 22, thereby constituting a reception signal processing unit.
The TDD system in the wireless transceiver system according to the prior art illustrated in FIG. 1 divides time so that transmission and reception of signals are alternately performed, wherein a single antenna is used, and a switch or a circulator is used for time-dividedly choosing between transmission and reception. Furthermore, one local oscillator is used because the same frequency band is used when transmitting and receiving signals.
FIG. 2 is a general schematic diagram of a wireless transceiver system wherein the prior FDD system is applied.
As shown in FIG. 2, a wireless transceiver system using the prior FDD system includes a first low pass filter 32, a first local oscillator 33, a first mixer 34, a first band-pass filter 35, a power amplifier 36, a duplexer 37, and an antenna Ant, thereby constituting a transmission signal processing unit.
Also, the wireless transceiver system using the prior FDD system includes an antenna Ant, a duplexer 37, a low-noise amplifier 38, a second band-pass filter 39, a second local oscillator 40, a second mixer 41, and a second low pass filter 42, thereby constituting a reception signal processing unit.
The FDD system in the wireless transceiver system according to the prior art illustrated in FIG. 2 uses two distinct frequencies for transmission and reception of signals, for which two different local oscillators, a transmission local oscillator and a reception local oscillator, are adopted. Therefore, in terms of time, transmission and reception are carried out simultaneously, and frequencies are divided into a transmission frequency and a reception frequency using a duplexer, which is a filter of a frequency band, and a signal of the transmission frequency is transmitted through the antenna while a signal of the reception frequency is received.
According to the various next generation wireless communication standards provided at present, they are developing independently for the two communication systems described above, and they prescribe that different frequency bands should be used for the respective systems. This is for extensively taking advantage of the merit of efficient use of the limited frequency resource of the TDD system and the merit of transmitting more data per hour of the FDD system, and one or both of the two systems may be selectively adopted and used according to the standards. Also, according to the standards, an advantageous communication system may be selected considering the limited frequency resource as the case may be.
In order to support the TDD system and the FDD system described above in a wireless transceiver system, a scheme that includes both the configuration supporting the TDD system illustrated in FIG. 1 and the configuration supporting the FDD system illustrated in FIG. 2 at a front-end of the wireless transceiver system and selectively uses them has been suggested.
However, this is practically difficult to employ because two transmitting/receiving apparatuses are required at the front-end of a wireless transceiver system, which causes the system to be relatively too large.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.